Hi! It looks like you’ve installed quite a few custom brushes in the Zbrush startup list affecting the size of the brush menu? If so, remove most of them. Only brushes that you will use every session should be installed in the startup list. Most custom situational brushes should be installed in the Lightbox folders to be loaded on demand.
You could also reduce the Ui button size in Preferences> Interface > UI to try and fit more items on screen at once, although my point above is still good general advice.
If that’s not what’s going on here, apologies, and please elaborate further.